This invention relates to an apparatus such as a video tape recorder (VTR) in which a tape is wound on a tape guide drum through a specified angle (loading operation) to record information on or reproduce information from the tape, and more particularly, to a tape loading mechanism suitable for reducing the cost of the recording and reproducing apparatus.
The conventional tape loading mechanism such as used in a VTR, which is one of the applications of this invention, has the following drawbacks.
(1) The operation of the tape loading mechanism is complex and varied, requiring a large number of component parts. PA1 (2) To improve image quality, high precision is required for manufacture, assembly and coordination of the parts. PA1 (3) High reliability is required for maintaining the recorded information.
These inevitably have contributed to increasing the cost.
To overcome these problems, improvements on the VTR tape loading mechanisms have been proposed in (1) the Japanese Patent Application Laid-Open No. 62-232750, (2) the Japanese Patent Application Laid-Open No. 58-218066, and (3) the Japanese Patent Application Laid-Open No. 57-133558. The tape loading mechanisms proposed in these patent applications realized a certain measure of simplification in the mechanism and reduction in cost. The inventors of this invention already proposed, with other joint inventors, a novel tape loading mechanism which is described in U.S. patent application Ser. No. 259,324, now U.S. Pat. No. 4,985,788, and corresponding Korean Patent Application No. 1988-13516. When one considers making a further reduction in cost, the following problems must be tackled.
(1) In the tape loading mechanism proposed in the Japanese Patent Application Laid-Open No. 62-232750, the guide base, on which tape guiding members for winding the tape on the tape guide drum are mounted, is engaged with a so-called guide plate which controls the path of travel and the attitude of the guide base. This makes it necessary during the assembly of the mechanism that the guide base and the guide plate be assembled to engage each other before the assembly is installed into the mechanism. Thus, the assembly efficiency becomes inevitably poor, thereby increasing the cost.
(2) Another disadvantage of the mechanism of the Japanese Patent Application Laid-Open No. 62-232750 is a construction in which the full-width erase head for erasing unnecessary recorded information from the tape is moved during the tape loading operation. This process is taken to avoid mechanical interference between the incoming side guide base and the full-width erase head when the guide base is moved, and to wind the tape on the full-width erase head over a sufficient winding angle at the completion of loading operation. The use of this head moving type construction increases the number of parts and also demands high precision on those parts that support the head for accurate positioning of the full-width erase head after the tape loading is completed. These inevitably increase the cost of the mechanism.
(3) In the mechanism described in the Japanese Patent Application Laid-Open No. 58-218066, three members--one of paired tape guides (first and second guides), one of two moving rings (first and second rings) that drive the guides, and drive rings that drive the first and second rings--are stacked one upon the other so that they are rotatable concentrically. Similar to this construction, a mechanism which uses arc sliders in place of the rings is known. In such loading mechanisms, the rotating rings or arc drive members are held and positioned in the following manner. The position of these members in the radial direction is restricted by gears or rollers that receive their outer circumference by engaging with a gear formed on the outer circumference of these members. The vertical position is restricted by flanges formed integrally with the gears or rollers that clamp the rings or arc drive members.
The above conventional technique does not take into consideration the warping or deflection of the arc drive members by their own weight when holding them in position. When, for example, the arc drive member with a gear formed on its outer circumference is to be held in position, it must be basically supported at all times by three members, that is, a first gear that drives the arc drive member, a second gear that supports the outer circumference of the arc drive member, and a roller that supports the inner circumference of the arc drive member and is arranged at an intermediate position between the two gears. When, however, the arc drive member is rotated through a wide rotating angle and the drive or support gear engages with the starting or terminating end of the gear of the arc drive member, the other end of the arc drive member parts from the three supporting points, with the result that the arc drive member will warp or deflect at its ends due to its own weight, impact, gear backlash or play. This in turn will easily result in an interference or collision between the arc drive members or between the arc drive members and other members, causing operation failures.
The arc drive members must transmit a pressing force to the pair of tape guides to force them to specified positions. When, however, the direction in which the tape guide is pushed differs from a direction in which the arc drive member is rotated, for example, when the arc drive member is rotated parallelly to the cassette mounting plane and the tape guide is pushed in a direction inclined with respect to that plane, the arc drive member will receive a reaction acting in a direction opposite to that in which the tape guide is pressed, causing the arc drive member to deflect, leading to operation failures.
To forestall such operation failures requires many auxiliary parts, pushing up the cost of the mechanism.
(4) In the mechanism introduced in the Japanese Patent Application Laid-Open No. 57-133558, the tape guide is guided along a predetermined path by a T-shaped rail (guide member) and by a tape guide with a C-shaped clamping portion that engages with the rail. In an apparatus where the tape guiding members are arranged three-dimensionally, the tape guide must be moved along a complex route made up of a straight, curved, and inclined paths to avoid interference by the tape guiding members mounted on the chassis (such as a stationary head, vertical position restricting guide, rotating drum, etc.). Further, if an attempt is made to reduce the size of the travel route for the tape guide to make the mechanism compact and lightweight, the rail may be formed of plastic in small size. In that case, however, the rail has a limited rigidity and when the tape guide is stressed with an overload, the rail would be deformed with the result that the tape guide would contact the tape guiding members such as a rotating drum during the loading operation, causing the mechanism to stop or damaging the travel guide.
The rail and the tape guide are engaged with each other with a very small clearance. At the loading completion position, however, the tape guide has an increased clearance from the rail because the tape guide must be free from the restriction by the rail to be positioned by the catcher. Because of this greater clearance, the tape guide is pulled by the back tension of the tape immediately before the completion of the loading process and is thus greatly tilted contacting the rotating drum, causing damages to the rotating drum and head or even failing to enter into the catcher. Another drawback is that when the cassette is being loaded, the tape guide would incline outwardly from the cassette depending on the attitude of the apparatus and the clearance, so that the tape would fail to be loaded at a specified position. As a result, the misaligned tape is extracted stopping the operation of the mechanism.
On the other hand, when the clearance is made small, the rail made up of a plurality of different arcs cannot provide a uniform clearance for both small arcs and large arcs, causing the tape guide to stick.
To forestall these operation failures, a large number of auxiliary parts are needed, increasing the cost of the mechanism. These are the disadvantages of the conventional mechanisms.